Radio receiver for carrier aggregation

ABSTRACT

A radio receiver circuit ( 10 ) configurable to operate in a carrier-aggregation, CA, mode and in a non-CA mode is disclosed. It comprises a first receive path ( 30 ) arranged to be operatively connected to an antenna ( 15 ) and a second receive path ( 40 ) arranged to be operatively connected to the same antenna ( 15 ). It further comprises a control unit ( 50 ) operatively connected to the first receive path ( 30 ) and the second receive path ( 40 ). In the CA mode, the control unit ( 50 ) controls the first receive path ( 30 ) to receive a first CC ( 6 ) and the second receive path to receive a second CC ( 8 ). In the non-CA mode, the control unit ( 50 ) selectively controls the first receive path ( 30 ) and the second receive path ( 40 ) to both receive the same single CC ( 6 ).

TECHNICAL FIELD

The present invention relates to radio receiver circuits capable ofoperation in carrier-aggregation scenarios.

BACKGROUND

In cellular communications networks, wireless terminals, sometimesreferred to as UEs (User Equipment), communicate wirelessly with basestations of the cellular communications network. In the downlink, fromthe base station to the UE, the UE may receive signals in a singlefrequency band associated with a single radio-frequency (RF) carrier. Inorder to improve the capacity (e.g. in terms of downlink bitrate), theconcept of carrier aggregation (CA) has been introduced in 3GPP (3rdGeneration Partnership Program) standards. Using CA, the UE maysimultaneously receive a plurality of RF carriers. These RF carriers arenormally referred to as component carriers, or CCs. On each CC there ismodulated an information signal, e.g. an OFDMA (Orthogonal FrequencyDivision Multiple Access) signal or a CDMA (Code-Division MultipleAccess) signal, carrying payload data and/or control information. TheCCs may be located within the same operating frequency band, in whichcase the CA is referred to as intra-band CA. Alternatively, the CCs maybe located within different operating frequency bands, in which case theCA is referred to as inter-band CA. For intra-band CA, the plurality ofCCs may be located contiguously (in frequency), in which case the CA isreferred to as contiguous CA, or may be non-contiguously located (infrequency) with frequency gaps in between, in which case the CA isreferred to as non-contiguous CA. In one scenario, the UE may beallocated a primary CC (PCC) associated with a primary cell (PCell) ofthe cellular communications network. When an increase in downlinkcapacity is needed, for whatever reason, the UE may additionally beallocated one or more secondary CCs (SCCs) associated with respectivesecondary cells (SCells).

One solution for enabling the UE to receive a plurality of CCs,particularly in a non-contiguous CA scenario, is to use a receivercircuit with a plurality of receive paths, each connected to the sameantenna, e.g. via a common low-noise amplifier (LNA). Each receive pathmay be responsible for reception of a particular one of the plurality ofCCs. For example, each receive path may be of direct-conversion type,comprising a mixer unit driven by an LO signal having a frequencyselected such that the mixer unit directly down-converts the particularCC to base band. The LO-signal frequency of each processing path maythus be selected in dependence of the RF frequency of the CC it is setto receive.

SUMMARY

Embodiments of the present invention are based on an insight thatreceiver circuitry intended for CA operation may be efficiently reusedin non-CA (or “single carrier”) operation for boosting the performance.

According to a first aspect, there is provided a radio receiver circuitconfigurable to operate in a CA mode, wherein the radio receiver circuitis to receive a plurality of component carriers (CCs), and in a non-CAmode, wherein the radio receiver circuit is to receive a single CC. Theradio receiver circuit comprises a first receive path arranged to beoperatively connected to an antenna and a second receive path arrangedto be operatively connected to the same antenna. Furthermore, the radioreceiver circuit comprises a control unit operatively connected to thefirst receive path and the second receive path. The control unit isadapted to, in the CA mode, control the first receive path to receive afirst CC of said plurality of CCs and control the second receive path toreceive a second CC, separate from the first CC, of said plurality ofCCs. Moreover, the control unit is adapted to, in the non-CA mode,selectively control the first receive path and the second receive pathto both receive the same single CC.

The radio receiver circuit may comprise a low-noise amplifier arrangedto operatively connect both the first receive path and the secondreceive path to the antenna.

The first receive path may comprise a mixer unit arranged to be drivenby a first local oscillator (LO) signal. The second receive path maycomprise a mixer unit arranged to be driven by a second LO signal. Thecontrol unit may be adapted to, in the CA mode, control the frequency ofthe first LO signal to enable reception of the first CC by the firstreceive path and control the frequency of the second LO signal to enablereception of the second CC by the second receive path.

The control unit may be adapted to, in the non-CA mode and in order toenable reception of the same single CC by both the first receive pathand the second receive path, control the frequency of the first LOsignal to be the same as the frequency of the second LO signal.

The radio receiver circuit may comprise processing circuitry arrangedto, in the non-CA mode, combine an output signal of the first receivepath with an output signal of the second receive path, therebygenerating a combined output signal. The control unit may be adapted to,in the non-CA mode, control at least one of a gain and a frequencybandwidth of the first receive path to be the same as that of the secondreceive path when the first receive path and the second receive path arecontrolled to both receive the same signal in said single frequency band

The radio receiver circuit may comprise processing circuitry arrangedto, in the non-CA mode, separately process an output signal of the firstreceive path and an output signal of the second receive path, therebygenerating a first processed signal and a second processed signal,respectively. The control unit may be adapted to, in the non-CA mode,control a gain of one of the first receive path and the second receivepath to be higher than a gain of the other one of the first receive pathand the second receive path when the first receive path and the secondreceive path are controlled to both receive the same single CC. Theprocessing circuitry may be arranged to perform signal-strengthmeasurements on the output signal from the first receive path and on theoutput signal from the second receive path, for example to determine again setting to be used during further reception in the non-CA mode.

The control unit may be adapted to, in the non-CA mode, selectivelydisable the second receive path.

The radio receiver circuit may be adapted to operate in a cellularcommunication system.

According to a second aspect, there is provided a radio communicationapparatus comprising a radio receiver circuit according to the firstaspect and an antenna, to which both the first receive path and thesecond receive path of the radio receiver circuit are operativelyconnected.

The radio communication apparatus may be a terminal for a cellularcommunication system. The terminal may for example be a mobiletelephone, a tablet computer, a portable computer, or a machine-typecommunication device.

According to a third aspect, there is provided a method of operating aradio receiver circuit configurable to operate in a CA mode, wherein theradio receiver circuit is to receive a plurality of component carriers(CCs), and in a non-CA mode, wherein the radio receiver circuit is toreceive a single CC. The radio receiver circuit comprises a firstreceive path operatively connected to an antenna, a second receive pathoperatively connected to the same antenna, and a control unitoperatively connected to the first receive path and the second receivepath. The method comprises controlling, in the CA mode and by thecontrol unit, the first receive path to receive a first CC of saidplurality of CCs and the second receive path to receive a second CC,separate from the first CC, of said plurality of CCs. Furthermore, themethod comprises selectively controlling, in the non-CA mode and by thecontrol unit, the first receive path and the second receive path to bothreceive the same single CC.

According to a fourth aspect, there is provided a computer programproduct comprising computer program code for executing the methodaccording to the third aspect when said computer program code isexecuted by the control unit of the radio receiver circuit

According to a fifth aspect, there is provided a computer readablemedium (such as a non-transitory computer readable medium) having storedthereon a computer program product comprising computer program code forexecuting the method according to the third aspect when said computerprogram code is executed by the control unit of the radio receivercircuit. The computer readable medium may e.g. be a non-transitorycomputer readable medium.

Further embodiments are defined in the dependent claims. It should beemphasized that the term “comprises/comprising” when used in thisspecification is taken to specify the presence of stated features,integers, steps, or components, but does not preclude the presence oraddition of one or more other features, integers, steps, components, orgroups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of embodiments of the inventionwill appear from the following detailed description, reference beingmade to the accompanying drawings, in which:

FIGS. 1-2 illustrate scenarios in which embodiments of the presentinvention may be employed;

FIGS. 3-8 show block diagrams according to embodiments of the presentinvention;

FIGS. 9-10 show flow charts according to embodiments of the presentinvention; and

FIG. 11 schematically illustrates a computer-readable medium and acontrol unit.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate communication environments wherein embodimentsof the present invention may be employed.

In FIG. 1, a radio-communication apparatus 1, illustrated as a terminal1 for a cellular communication system, is in wireless communication witha cellular communication system in a carrier aggregation (CA) mode. Inthe figures, the terminal 1 is depicted as a mobile telephone (or“cellular telephone”, such as a so called smartphone), but it can alsobe any other type of terminal for a cellular communication system, suchas a tablet computer, a portable computer, or a machine-typecommunication device (e.g. a sensor, sensor system, or similar arrangedto communicate via a cellular communication system). For brevity, theradio-communication apparatus 1 is in the following referred to as “theterminal 1”. In the CA mode, a radio-receiver circuit (further describedbelow) of the terminal 1 is arranged to receive a plurality of(downlink) component carriers (CCs), which may be contiguous ornon-contiguous. Normally, one of the CCs is a PCC of a PCell (describedin the background section above), and the other CCs are SCCs of SCells(also described in the background section above). In FIG. 2, theplurality of CCs comprises a first frequency CC 6 at a first (RF)carrier frequency f1 and a second CC 8, which is separate from the firstCC 6, at a second (RF) carrier frequency f2. The first CC 6 may e.g. bethe PCC, and the second CC 8 may e.g. be an SCC, or vice versa. Ingeneral, as there may be more than one SCell, there may be more than twoCCs in the plurality of CCs. In FIG. 1, the first CC 6 is illustrated astransmitted from a first base station 2, and the second CC 8 isillustrated as transmitted from a second base station 3, but in generalthey may also be transmitted from the same base station. The basestation or base stations 2, 3 may e.g. be from the group of macro basestations, such as a NodeB of a UTRAN (Universal Terrestrial Radio AccessNetwork) or an eNodeB of an eUTRAN (evolved UTRAN), micro, pico, andfemto base stations, but may also be other kinds of current or futurebase stations. Furthermore, in FIG. 1, the first and second CCs 6,8 areillustrated as non-contiguous (or non-adjacent) CCs having a frequencygap between them, but in other embodiments or scenarios, they may becontiguous (or adjacent) CCs.

In FIG. 2, the terminal 1 is in wireless communication with the cellularcommunication system in a non-CA mode. In the non-CA mode, the radioreceiver circuit of the terminal 1 is arranged to receive a single CC.In FIG. 2, the single CC is illustrated as the same CC as the first CC 6from the first base station 2 in FIG. 1, but may well be some other CC(such as but not limited to the second CC 8 in FIG. 1) and/or from someother base station (such as but not limited to the second base station 3in FIG. 1).

FIG. 3 shows a simplified block diagram of a part of the terminal 1according to an embodiment. The above-mentioned radio receiver circuitis denoted with reference number 10. It is operatively connected to anantenna 15 of the terminal 10 via an antenna port 20 of the radioreceiver circuit 10. The terminal 1 may naturally also comprise manyother parts as well, such as one or more transmitters, one or moreprocessors, input and output devices (e.g. buttons, displays,touchscreens, etc), etc. For simplicity, such other parts are not shownin FIG. 3.

In FIG. 3, the terminal 1 is illustrated as having a single antenna 15.In other embodiments, the terminal 1 may have multiple antennas. Forexample, the terminal 1 may have multiple receive antennas for diversityreception. This is illustrated in FIG. 4, which shows a simplified blockdiagram of another embodiment of the terminal 1. As in the embodiment ofFIG. 1, the embodiment of the terminal 1 in FIG. 4 comprises the radioreceiver circuit 10 operatively connected to the antenna 15 of theterminal 1 via the antenna port 20 of the radio receiver circuit 10. Inaddition, the terminal 1 comprises another radio receiver circuit 10′and another antenna 15′, wherein the radio receiver circuit 10′ isoperatively connected to the antenna 15′ of the terminal 1 via anantenna port 20′ of the radio receiver circuit 10′. In the following,embodiments of the radio receiver circuit 10 are described. The radioreceiver circuit 10′ may e.g. be designed in the same way as the radioreceiver circuit 10.

FIG. 5 shows a block diagram of an embodiment of the radio receivercircuit 10. As indicated above, the radio receiver circuit 10 isconfigurable to operate in a CA mode, wherein the radio receiver circuit10 is to receive a plurality of CCs, such as the CCs 6 and 8 (FIG. 1).Furthermore, the radio receiver circuit 10 is configurable to operate ina non-CA mode, wherein the radio receiver circuit 10 is to receive asingle CC, such as the CC 6 (FIG. 2). The radio receiver circuit 10 mayfor example be adapted to operate in a cellular communication system.

The radio receiver circuit 10 comprises a first receive path 30 arrangedto be operatively connected to the antenna. In the embodimentillustrated in FIG. 5, the first receive path 30 has an input port 32arranged to be operatively connected to the antenna 15. Furthermore, inthe embodiment illustrated in FIG. 5, the first receive path 30 has anoutput port 34 arranged to provide an output signal of the first receivepath 30.

Furthermore, the radio receiver circuit 10 comprises a second receivepath 40 arranged to be operatively connected to the same antenna 15. Inthe embodiment illustrated in FIG. 5, the second receive path 40 has aninput port 42 arranged to be operatively connected to the antenna 15.Furthermore, in the embodiment illustrated in FIG. 5, the second receivepath 40 has an output port 44 arranged to provide an output signal ofthe second receive path 40.

In the embodiment illustrated in FIG. 5, the radio receiver circuit 10comprises an LNA (Low-Noise Amplifier) 60 common to the first receivepath 30 and the second receive path 40. The LNA 60 is arranged tooperatively connect both the first receive path 30 and the secondreceive path 40 to the antenna 15, via the antenna port 20 of the radioreceiver circuit 10. In other embodiments, the radio receiver circuit 10may comprise separate LNAs arranged to operatively connect the firstreceive path 30 and the second receive path 40, respectively, to theantenna 15, via the antenna port 20 of the radio receiver circuit 10.

The radio receiver circuit 10 further comprises a control unit 50operatively connected to the first receive path 30 and the secondreceive path 40 for controlling the operation of the first receive path30 and the second receive path 40. Moreover, in the embodimentillustrated in FIG. 5, the radio receiver circuit 10 comprisesprocessing circuitry 70 operatively connected to the first receive path30 and the second receive path 40 and arranged to process the outputsignals from the first receive path 30 and the second receive path 40.As illustrated in FIG. 5, the processing circuitry 70 may have an inputport 72 connected to the output port 34 of the first receive path 30,and an input port 74 connected to the output port 44 of the secondreceive path 40. The processing circuitry 70 may for example comprise,be, or be part of a digital signal processor, such as a basebandprocessor of the radio receiver circuit 10. Similarly, the control unit50 may comprise, be, or be part of a digital signal processor, such as abaseband processor of the radio receiver circuit 10, potentially thesame digital signal processor as for the processing circuitry 70mentioned in the preceding sentence.

The control unit 50 is adapted to, in the CA mode, control the firstreceive path 30 to receive a first CC 6 of said plurality of frequencybands and control the second receive path to receive a second CC 8 ofsaid plurality of CCs. The processing circuitry 70 can then process theoutput signals from the first receive path 30 and the second receivepath 40, e.g. according to well-known techniques, including for exampledemodulation and decoding of the output signals, to recover the datatransmitted on the signals in the respective frequency bands.

The inventors have realized that, in the non-CA mode, hardware used forCA-reception in the CA mode can be efficiently reused for increasing thedynamic range of the radio receiver circuit 10 in situations where suchan increased dynamic range is needed. Examples of such situationsidentified by the inventors are situations where the received signal isrelatively weak, situations with presence of blocking interferer(s), andduring signal measurements when the strength of the received signal isinitially unknown to the radio receiver circuit 10. This can be achievedby, in the non-CA mode, controlling both the first receive path 30 andthe second receive path 40 to both receive the same single CC 6. Thereare different alternatives for how the processing circuitry 70 canprocess the output signals from the first receive path and the secondreceive path, examples of which are described further below in thecontext of various embodiments. Accordingly, in accordance withembodiments of the present invention, the control unit 50 is adapted to,in the non-CA mode, selectively control the first receive path 30 andthe second receive path 40 to both receive the same single CC 6.

Using both the first receive path 30 and the second receive path 40 toboth receive the same single CC 6 leads to a higher power consumptioncompared with using only one of the receive paths (say the first receivepath 30) while disabling the other receive path (say the second receivepath 40). Therefore, according to some embodiments, it is suggested toavoid using both the first receive path 30 and the second receive path40 to both receive the same single CC 6 unless the additional dynamicrange provided by doing so is actually needed. Therefore, according tosome embodiments, the control unit 50 is adapted to, in the non-CA mode,selectively disable the second receive path 40.

FIG. 6 is a block diagram of an embodiment of the radio receiver circuit10, showing some more details than the block diagram in FIG. 5. Asillustrated in FIG. 6, the first receive path 30 may comprise a mixerunit 100 arranged to be driven by a first local oscillator (LO) signal.Furthermore, as illustrated in FIG. 6, the second receive path 40 maycomprise a mixer unit 200 arranged to be driven by a second LO signal.To facilitate CA reception, the control unit 50 may be adapted to, inthe CA mode, control the frequency of the first LO signal to enablereception of the first CC 6 by the first receive path 30 and control thefrequency of the second LO signal to enable reception of the second CC 8by the second receive path 40.

In some embodiments, the first LO signal and the second LO signal aredistinct LO signals generated by distinct LO units. For example, asillustrated in FIG. 6, the first receive path 30 may comprise a LO unit110 arranged to generate the first LO signal, and the second receivepath 40 may comprise a separate LO unit 210 arranged to generate thesecond LO signal. The first receive path 30 and the second receive path40 may then, for example, both operate as direct conversion receivers.In that case, the control unit 50 may be adapted to, in the CA mode,control the frequency of the first LO signal and the frequency of thesecond LO signal to be equal, or approximately equal, to the centerfrequency f1 of the first CC 6 and the center frequency f2 of the secondCC 8, respectively. Furthermore, in order to enable reception of thesame single CC 6 by both the first receive path 30 and the secondreceive path 40 in the non-CA mode, the control unit 50 may be adaptedto, in the non-CA mode, control the frequency of the first LO signal tobe the same as the frequency of the second LO signal. This samefrequency may, for instance, be equal, or approximately equal, to thecenter frequency f1 of the single CC 6, in which case both the firstreceive path 30 and the second receive path 40 are arranged to operateas direct-conversion receivers.

In some embodiments, the first LO signal and the second LO signal may,at least in the non-CA mode, be the same LO signal, generated by acommon LO unit (e.g. the LO unit 110 or the LO unit 210 in FIG. 6)comprised in the radio receiver circuit 10.

The LO units mentioned above may be any kind of suitable circuit capableof synthesizing the LO signals in question. For example, the LO unitsmay be or comprise a phase-locked loop (PLL) or similar circuit. Suchcircuits are well-known in the art of radio receiver circuit design andare therefore not described in any further detail.

In some embodiments, the mixer units 100 and 200 (FIG. 6) areimplemented as quadrature mixers. Quadrature mixers are capable ofrejecting image-signal components generated in the down-conversionprocess, and are therefore beneficially used in many radio receivercircuits. A quadrature mixer has an in-phase (I) branch, arranged togenerate an I output signal of the quadrature mixer and comprising amixer, referred to as the I mixer, driven by an I component of the LOsignal. Furthermore, a quadrature mixer has a quadrature-phase (Q)branch, arranged to generate a Q output and comprising a mixer, referredto as the Q mixer, driven by a Q component of the LO signal. The I and Qcomponents of the LO signal both have the same frequency, but a mutual90-degree (or π/4 rad) phase shift. An LO signal comprising an I and a Qcomponent can be referred to as a quadrature LO signal. The LO unitsmentioned above might therefore be quadrature LO units, i.e. LO unitscapable of generating quadrature LO signals. Such quadrature LO unitsare well known in the art of radio receiver circuit design and thereforenot described in any further detail.

As is further illustrated in FIG. 6, the first receive path 30 maycomprise a filter unit 120 operatively connected, at an input port ofthe filter unit 120, to an output port of the mixer unit 100.Furthermore, as is also illustrated in FIG. 6, the first receive path 30may comprise an analog-to-digital converter (ADC) unit 130 operativelyconnected, at an input port of the ADC unit 130, to an output port ofthe filter unit 120. The ADC unit 130 may be arranged to generate theoutput signal of the first receive path 30 as a digital output signal onthe output port 34 of the first receive path 30. The filter unit 120 maybe arranged to perform one or more of the tasks of: channel selectionfiltering and acting as an anti-aliasing filtering for the ADC unit 130.In embodiments where the mixer unit 100 is a quadrature mixer, thefilter unit 120 may comprise a separate filter for each of the I and theQ branch, and similarly, the ADC unit 130 may comprise a separate ADCfor each of the I and Q branch.

Similarly, as is also illustrated in FIG. 6, the second receive path 40may comprise a filter unit 220 operatively connected, at an input portof the filter unit 220, to an output port of the mixer unit 200.Furthermore, as is also illustrated in FIG. 6, the second receive path40 may comprise an ADC unit 230 operatively connected, at an input portof the ADC unit 230, to an output port of the filter unit 220. The ADCunit 230 may be arranged to generate the output signal of the secondreceive path 40 as a digital output signal on the output port 44 of thesecond receive path 40. The filter unit 220 may be arranged to performone or more of the tasks of: channel selection filtering and acting asan anti-aliasing filtering for the ADC unit 230. In embodiments wherethe mixer unit 200 is a quadrature mixer, the filter unit 220 maycomprise a separate filter for each of the I and the Q branch, andsimilarly, the ADC unit 230 may comprise a separate ADC for each of theI and Q branch.

In some embodiments, the dynamic range (in the non-CA mode) can beincreased by combining, or summing, the output signal of the firstreceive path 30 with the output signal of the second receive path 40,thereby generating a combined output signal. Each of the output signalfrom the first receive path 30 and the output signal from the secondreceive path 40 comprises a desired signal component and an undesiredsignal component (e.g. noise and distortion). When combining the outputsignals from the first and the second receive paths, the desired signalcomponents in these output signals will combine constructively in thecombined output signal, whereby at least uncorrelated parts (typicallyarising from noise, such as thermal noise) of the undesired signalcomponents of these output signals will be effectively suppressedcompared with the desired signal components in the combined outputsignal. In order for such suppression to be efficient, the output signalfrom the first receive path and the output signal from the secondreceive path should have a relatively small mutual phase difference. Forthe best performance, they should be combined in phase with each other.In phase, in this context, does not mean “exactly in phase”, becausethat is not possible to achieve in practice, e.g. due to noise andlimited computational precision, but should be interpreted as“approximately in phase” (within tolerances that depend on theimplementation). With increasing mutual phase difference between theoutput signals from the first receive path 30 and the second receivepath 40, the performance gain diminishes.

Assuming that the gain of the first and the second receive path 30, 40are equal and their output signals are combined exactly in phase(referred to below as “the ideal case”), and that the unwanted signalcomponents in the output signals of the first receive path 30 and thesecond receive path 40 are uncorrelated, an improvement in dynamic rangewith approximately 3 dB is obtained compared with the individual outputsignal from one of the first receive path 30 and the second receive path40. If they are instead combined out-of phase with a phase difference φ,the magnitude of the desired signal component in the combined outputsignal will be scaled with a factor cos(φ/2) compared with the idealcase, and the corresponding signal power of the desired signal componentwill thus change with 20 log₁₀ cos(φ/2) dB compared with the ideal case,whereas the signal power of the uncorrelated unwanted signal componentswill stay unchanged compared with the ideal case. Thus, also the dynamicrange will change with 20 log₁₀ cos(φ/2) compared with the ideal case.For example, if φ=20 degrees, the dynamic range is reduced 0.13 dBcompared with the ideal case. Thus, even with a relatively large phasedifference such as 20 degrees, an improvement as large as 2.87 dB isobtainable.

Accordingly, in some embodiments of the present invention, theprocessing circuitry 70 is arranged to, in the non-CA mode, combine theoutput signal of the first receive path 30 with the output signal of thesecond receive path 40, thereby generating the combined output signal.In some of these embodiments the processing circuitry 70 is arranged to,in the non-CA mode, combine the output signal of the first receive path30 in phase with the output signal of the second receive path 40,thereby generating the combined output signal.

FIG. 7 illustrates an embodiment of the processing circuitry 70 arrangedto combine the output signal from the first receive path 30 and thesecond receive path 40. As illustrated in FIG. 7, the processingcircuitry 70 may comprise a phase adjust unit 310 adapted to adjust thephase of the output signal from the first receive path 30. Additionallyor alternatively, the processing circuitry 70 may comprise a phaseadjust unit 320 adapted to adjust the phase of the output signal fromthe second receive path 40. The phase adjust unit 310 and/or the phaseadjust unit 320 may be adapted to adjust the phase of the output signalfrom the first receive path 30 and/or the output signal from the secondreceive path, respectively, such that they are in phase with each otherbefore combining. Furthermore, as illustrated in FIG. 7, the processingcircuitry 70 may comprise an adder unit 330 arranged to generate thecombined output signal on an output 340 of the adder unit 330 bycombining, or adding, the (optionally phase adjusted) output signalsfrom the first receive path 30 and the second receive path 40. Inembodiments where the processing circuitry 70 is implemented by means ofa digital signal processor, any of the units 310, 320, and 330 may beimplemented in software on the digital signal processor.

The phase adjust units 310 and 320 are indicated in FIG. 7 as beingoptional. In some embodiments, only one of them is included.Furthermore, in some embodiments, the output signals from the firstreceive path 30 and the second receive path 40 are already adequatelyphase aligned such that no phase adjustment is needed in the processingcircuitry 70. For example, in embodiments where the mixer units 100 and200 (FIG. 6) are arranged to be driven with a common LO signal in thenon-CA mode, an adequate phase alignment between the output signals fromthe two receive paths 30 and 40 can be provided, provided that the tworeceive paths are relatively well matched. Alternatively, in embodimentswhere the mixer units 100 and 200 (FIG. 6) are arranged to be drivenwith separate LO signals from the LO units 110 and 210 (FIG. 6), thecontrol unit 50 can be arranged to control the LO units 110 and 210 inorder to phase align the LO signals such that an adequate phasealignment of the output signals from the two receive paths 30 and 40 isprovided.

Detection of a phase difference between the output signals from thefirst receive path 30 and the second receive path can be performed bycorrelating these output signals, for example in the processingcircuitry 70. Hence, in some embodiment, the processing circuitry 70 maybe adapted to derive the phase difference, e.g. by correlating theoutput signals from the first receive path 30 and the second receivepath with each other.

However, at relatively weak signal levels or in presence of relativelystrong interferers (which are situations where using more than onereceive path for receiving the same single CC 6 may be particularlybeneficial) the convergence of such a correlation method might berelatively slow. In some embodiments, this might therefore not besufficiently good. Another alternative that can be faster is to utilizethe LO signals from the LO units 110 and 210 to detect the phasedifference between the output signals from the first receive path 30 andthe second receive path 40, e.g. by means of a time-to-digital converter(not shown) arranged to measure a time difference between the arrival(such as the arrival of a falling or rising edge) of the LO signals fromthe LO units 110 and 120. Accordingly, in some embodiments, the controlunit 50 or the processing circuitry 70 is adapted to derive the phasedifference between the output signals from the first receive path 30 andthe second receive path 40 based on the LO signals from the LO unit 110and the LO unit 210.

Regardless of how the phase difference between output signals from thefirst receive path 30 and the second receive path is derived, theprocessing circuitry 70 may be adapted to adjust the phase(s) of theoutput signal from the first receive path 30 and/or the output signalfrom second receive path 40 based on the derived phase difference, forexample by means of the phase adjust unit 310 and/or the phase adjustunit 320. Alternatively, the control unit 50 may be adapted to controlthe LO unit 110 and/or the LO unit 120 to phase align the LO signalsfrom the LO units 110 and 210.

Regardless of how the phase difference is detected and adjusted, itshould be noted from the calculations above that the requirement onphase accuracy is normally relatively relaxed. For example, using theformula 20 log₁₀ cos(φ/2) dB for the dynamic-range degradation derivedabove, it can be concluded that if, for example, a 0.3 dB degradation(compared with the ideal case) could be acceptable, an absolute phasedifference of almost 30 degrees would be OK. Thus, the detection of andadjustment of the phase difference can be made relatively coarse, whichis advantageous from an implementation perspective.

The control unit 50 may be adapted to, in the non-CA mode, control atleast one (in some embodiments both) of a gain and a frequency bandwidthof the first receive path 30 to be the same as that of the secondreceive path 40 when the first receive path 30 and the second receivepath 40 are controlled to both receive the same single CC 6. Forexample, the filter units 120 and 220 might have a controllable gain (orattenuation) and/or a controllable frequency bandwidth. The control unit50 may be adapted to control the gain and/or frequency bandwidth of thefirst receive path 30 and the second receive path 40 by controlling thefilter units 120 and 220.

Above, embodiments have been described wherein the processing circuitry70 is adapted to combine the output signals from the first receive path30 and the second receive path 40. In other embodiments, the processingcircuitry 70 is arranged to, in the non-CA mode, separately process anoutput signal of the first receive path 30 and an output signal of thesecond receive path 40, thereby generating a first processed signal anda second processed signal, respectively. This is illustrated in FIG. 8,wherein the processing circuitry 70 comprises a first processing path350 arranged to separately process the output signal from the firstreceive path 30 and a second processing path 360 arranged to separatelyprocess the output signal from the second receive path 40. Processing ofan output signal from a receive path may in this context e.g. includewell-known operations such as but not limited to equalization,demodulation and decoding. It may also, as is further described below,include making signal-strength measurements.

In some situations, the power of the desired signal is unknown. Anexample of such a situation is when the terminal 1 performsmeasurements. For example, the terminal 1 may be connected to a servingcell, but periodically make measurements on neighboring cells, e.g. inorder to facilitate identification of suitable targets cells forhandover or for use as SCells. For a given gain setting of a receivepath, the receive path has a certain dynamic range, i.e. range of inputsignal power levels that it is capable of handling. For an input signalpower level below a lower threshold of the dynamic range, the signalwould be hidden in noise and other unwanted signal components in thereceive path. For an input signal power level above an upper thresholdof the dynamic input range, the signal would saturate, or clip, in thereceive path. The dynamic range depends on the gain setting of thereceive path; with increasing gain, the receive path is capable ofhandling lower input signal power levels, but at the same time startsclipping, or saturating, at a lower input signal power level as well.

In such situations as mentioned above, wherein the power of the desiredsignal is unknown, the dynamic range of the radio receiver circuit 10can be increased by selecting different gain settings for the firstreceive path 30 and the second receive path 40, and processing theoutput signal from the first receive path 30 and the output signal fromthe second receive path 40 separately. By using different gain settings,the two receive paths 30 and 40 together cover a larger range ofpossible input signal power levels than a single receive path would.

For the sake of illustration, consider the case when the gain of thefirst receive path 30 is set higher than the gain of the second receivepath 40 (although it may well be the other way around in someembodiments), and wherein the dynamic ranges of the first receive path30 and the second receive path 40 partially overlap, such that there isan overlapping range of input signal power levels that can be handled byboth receive paths 30 and 40. Then there is a lower range of inputsignal power levels below that overlapping range that cannot be handledby the second receive path 40, but can be handled by the first receivepath 30. There is also an upper range of input signal power levels abovethat overlapping range that cannot be handled by the first receive path30, but can be handled by the second receive path 40. The combineddynamic range of the first receive path 30 and the second receive path40 is then the union of the lower range, the overlapping range, and theupper range (which is the union of the dynamic range of the firstreceive path 30 and the second receive path 40). This combined dynamicrange is larger than the dynamic range of the first receive path 30 andthe dynamic range of the second receive path 40 individually.

Accordingly, in some embodiments, the control unit 50 is adapted to, inthe non-CA mode, control a gain of one of the first receive path 30 andthe second receive path 40 to be higher than a gain of the other one ofthe first receive path 30 and the second receive path 40 when the firstreceive path and the second receive path are controlled to both receivethe same single CC 6. In some embodiments, the control unit 50 may beadapted to set the gain of said one of the receive paths 30, 40 to thehighest possible gain and the gain of said other one of the receivepaths 30, 40 to the lowest possible gain, thereby providing the maximumachievable dynamic range available when using two receive paths in thismanner.

For the sake of comparison, consider use of a single receive path formaking signal strength measurements. In that case, depending on theinitial gain setting of the receive path and the input signal powerlevel, the gain might need to be adjusted iteratively in order to find again setting adequate for making a reliable measurement, whereby such ameasurement can be relatively slow. If instead two receive paths areused simultaneously with different gain settings as described above, theincreased dynamic range facilitates an increased measurement speed, withless required gain adjustments, if any at all. For example, if the gainof one of the receive paths 30 and 40 is set to the maximum possiblegain and the gain of the other one of the receive paths 30 and 40 is setto the minimum possible gain, then their combined dynamic range is suchthat at least one of the receive paths 30 and 40 can correctly detect aninput signal with any signal power level detectable with a singlereceive path, without having to perform any iterative gain adjustment(provided that the individual dynamic ranges of the receive paths 30 and40 overlap, such that there is no intermediate input signal power levelfor which none of the receive paths 30 and 40 can correctly detect theinput signal). For such a gain setting, the measurements can beperformed significantly faster than using a single receive path.

In cellular communication systems, measurements on neighboring cells canbe performed in a so called compressed mode. In the compressed mode,signal transmissions are scheduled with measurement gaps, where notransmission takes place from the serving base station to the terminal,in between. During such measurement gaps, the terminal is enabled tomake measurements on neighboring cells. By speeding up the measurementsas described above, the terminal will be able to complete themeasurements during shorter measurement gaps than would otherwise bepossible, thereby enabling decreasing the duration of the measurementgaps and allowing more data to be transmitted during compressed mode.Alternatively, if the duration of the measurement gaps are notdecreased, it enables more measurements to be made during eachmeasurement gap. Furthermore, the improved measurement speed can beutilized to quickly determine a correct gain setting to be used duringfurther reception in the non-CA mode.

Accordingly, in some embodiments, the processing circuitry 70 isarranged to perform signal-strength measurements on the output signalfrom the first receive path 30 and on the output signal from the secondreceive path 40. For example, the processing circuitry 70 may bearranged to perform signal-strength measurements on the output signalfrom the first receive path 30 and on the output signal from the secondreceive path 40 for determining a gain setting to be used during furtherreception in the non-CA mode. The processing circuitry 70 may be adaptedto communicate said determined gain setting to the control unit 50. Thecontrol unit 50 may be adapted to control the first receive path 30and/or the second receive path 40 to apply said determined gain settingduring further reception in the non-CA mode. In some embodiments,applying the determined gain setting during further reception in thenon-CA mode means applying the determined gain setting as an initialgain setting. The gain setting can then be further adjusted using anautomatic gain-control (AGC) algorithm during the further reception inthe non-CA mode, e.g. to account for varying reception conditions. AGCalgorithms are well known in the art of radio receiver design and arenot described herein in any further detail.

Above, some embodiments have been described where the processingcircuitry 70, in the non-CA mode, is arranged to combine the outputsignals from the first processing path 30 and the second processing path40. Furthermore, other embodiments have been described where theprocessing circuitry 70, in the non-CA mode, is arranged to process theoutput signals from the first processing path 30 and the secondprocessing path 40 separately. In some further embodiments, theprocessing circuitry 70 is arranged to do both. For example, during afirst time period in the non-CA mode, the control unit 50 can be adaptedto control the gain of one of the first receive path 30 and the secondreceive path 40 to be higher than the gain of the other one of the firstreceive path 30 and the second receive path 40, and the processingcircuitry 70 may be arranged to separately process the output signalsfrom the first receive path 30 and the second receive path 40 andperform signal strength measurements to determine a gain setting to beused during further reception in the non-CA mode. During a second timeperiod in the non-CA mode, after the first time period, the control unit50 may be adapted to control the first receive path 30 and/or the secondreceive path 40 to apply said determined gain setting, and theprocessing circuitry 70 may be adapted to combine the output signalsfrom the first receive path 30 and the second receive path. In someembodiments, depending on the signal strength, the control unit 50 maybe adapted to selectively disable one of the receive paths 30 and 40during the second time period for saving power.

According to some embodiments of the present invention, there isprovided a method of operating the radio receiver circuit 10. The methodcomprises controlling, in the CA mode and by the control unit 50, thefirst receive path 30 to receive a first CC 6 of said plurality of CCs6, 8 and the second receive path 40 to receive a second CC 8, separatefrom the first CC 6, of said plurality of CCs 6, 8. The method furthercomprises selectively controlling, in the non-CA mode and by the controlunit 50, the first receive path 30 and the second receive path 40 toboth receive the same single CC 6.

An embodiment of the method is illustrated with a flow chart in FIG. 9.The operation is started in step 400. In step 410, it is checked whetherthe radio receiver circuit 10 operates in the CA mode or the non-CAmode. If it operates in the CA mode (YES branch from step 410), thecontrol unit 50 controls the first receive path 30, in step 420, toreceive the first CC 6 and the second receive path 40, in step 430, toreceive the second CC 8. The operation of the method is then ended instep 440. If the radio receiver circuit 10 operates in the non-CA mode(NO branch from step 410), the control unit 50 selectively controls, instep 450, the first receive path 30 and the second receive path 40 toboth receive the same single CC 6. The operation of the method is thenended in step 440.

As indicated above in the context of embodiments of the radio receivercircuit 10, selectively controlling the first receive path 30 and thesecond receive path 40 to both receive the same single CC 6 can, in someembodiments, include controlling the first receive path 30 and thesecond receive path 40 to both receive the same single CC 6 when anincreased dynamic range (compared with using a single receive path) isneeded, and otherwise disabling the second receive path 40 for savingpower. As mentioned above, an increased dynamic range can e.g. be neededin situations where the received signal is relatively weak, situationswith presence of blocking interferer(s), and during signal measurementswhen the strength of the received signal is initially unknown to theradio receiver circuit 10. FIG. 10 is a flow chart for an embodiment ofstep 450 (FIG. 9). The operation of step 450 is started in step 500. Instep 510, it is checked by the control unit 50 whether an increaseddynamic range is needed. If so (YES branch from step 510), the controlunit 50 controls the first receive path 30 and the second receive path40 to both receive the same single CC 6. Then, the operation of step 450is ended in step 530. If not (NO branch from step 510), the control unit50 disables the second receive path 40 for saving power. Then, theoperation of step 450 is ended in step 530.

Embodiments of the present invention provides a capability for boostingthe dynamic range of a radio receiver circuit during non-CA operation byefficiently reusing circuitry intended for receiving multiple CCs duringCA operation. The reuse of circuitry intended for receiving multiple CCsusing CA operation for providing the boost in dynamic range isadvantageous, for instance in that relatively little overhead, e.g. interms of hardware, is needed for providing the boost in dynamic range.

In some embodiments, the control unit 50 may be implemented as adedicated application-specific hardware unit. Alternatively, the controlunit 50, or parts thereof, may be implemented with programmable and/orconfigurable hardware units, such as but not limited to one or morefield-programmable gate arrays (FPGAs), processors, or microcontrollers.Thus, the control unit 50 may be a programmable control unit. Hence,embodiments of the present invention may be embedded in a computerprogram product, which enables implementation of the method andfunctions described herein. Therefore, according to embodiments of thepresent invention, there is provided a computer program product,comprising instructions arranged to cause the programmable control unitto perform the steps of any of the embodiments of said methods. Thecomputer program product may comprise program code which is stored on acomputer readable medium 600, as illustrated in FIG. 11, which can beloaded and executed by said programmable control unit, to cause it toperform the steps of any of the embodiments of said methods. Thecomputer-readable medium 600 may e.g. be a non-transitorycomputer-readable medium.

The present invention has been described above with reference tospecific embodiments. However, other embodiments than the abovedescribed are possible within the scope of the invention. Differentmethod steps than those described above, performing the method byhardware or software, may be provided within the scope of the invention.The different features and steps of the embodiments may be combined inother combinations than those described. The scope of the invention isonly limited by the appended patent claims.

The invention claimed is:
 1. A radio receiver circuit configured tooperate in a carrier-aggregation (CA) mode, wherein the radio receivercircuit is to receive a plurality of component carriers (CCs) and in anon-CA mode, wherein the radio receiver circuit is to receive a singleCC, comprising: a first receive path arranged to be operativelyconnected to an antenna; a second receive path arranged to beoperatively connected to the same antenna; and a processing circuitoperatively connected to the first receive path and the second receivepath; wherein the processing circuit is adapted to, in the CA mode,control the first receive path to receive a first CC of said pluralityof CCs and control the second receive path to receive a second CC,separate from the first CC, of said plurality of CCs; and the processingcircuit is adapted to, in the non-CA mode, selectively control the firstreceive path and the second receive path to both receive the same singleCC.
 2. The radio receiver circuit of claim 1, comprising a low-noiseamplifier arranged to operatively connect both the first receive pathand the second receive path to the antenna.
 3. The radio receivercircuit of claim 1, wherein: the first receive path comprises a mixerunit arranged to be driven by a first local oscillator, LO, signal; thesecond receive path comprises a mixer unit arranged to be driven by asecond LO signal; the processing circuit is adapted to, in the CA mode,control the frequency of the first LO signal to enable reception of thefirst CC by the first receive path and control the frequency of thesecond LO signal to enable reception of the second CC by the secondreceive path.
 4. The radio receiver circuit of claim 3, wherein theprocessing circuit is adapted to, in the non-CA mode and in order toenable reception of the same single CC by both the first receive pathand the second receive path, control the frequency of the first LOsignal to be the same as the frequency of the second LO signal.
 5. Theradio receiver circuit of claim 1, wherein the processing circuit isarranged to, in the non-CA mode, combine an output signal of the firstreceive path with an output signal of the second receive path, therebygenerating a combined output signal.
 6. The radio receiver circuit ofclaim 5, wherein the processing circuit is adapted to, in the non-CAmode, control at least one of a gain and a frequency bandwidth of thefirst receive path to be the same as that of the second receive pathwhen the first receive path and the second receive path are controlledto both receive the same single CC.
 7. The radio receiver circuit ofclaim 1, wherein the processing circuit is arranged to, in the non-CAmode, separately process an output signal of the first receive path andan output signal of the second receive path, thereby generating a firstprocessed signal and a second processed signal, respectively.
 8. Theradio receiver circuit of claim 7, wherein the processing circuit isadapted to, in the non-CA mode, control a gain of one of the firstreceive path and the second receive path to be higher than a gain of theother one of the first receive path and the second receive path when thefirst receive path and the second receive path are controlled to bothreceive the same single CC.
 9. The radio receiver circuit of claim 8,wherein the processing circuit is arranged to perform signal-strengthmeasurements on the output signal from the first receive path and on theoutput signal from the second receive path.
 10. The radio receivercircuit of claim 9, wherein the processing circuit is arranged toperform said signal-strength measurements to determine a gain setting tobe used during further reception in the non-CA mode.
 11. The radioreceiver circuit of claim 1, wherein the processing circuit is adaptedto, in the non-CA mode, selectively disable the second receive path. 12.The radio receiver circuit of claim 1, wherein the radio receivercircuit is adapted to operate in a cellular communication system.
 13. Aradio communication apparatus comprising: the radio receiver circuit ofclaim 1; and an antenna, to which both the first receive path and thesecond receive path of the radio receiver circuit are operativelyconnected.
 14. The radio communication apparatus of claim 13, whereinthe radio communication apparatus is a terminal for a cellularcommunication system.
 15. The radio communication apparatus of claim 14,wherein the terminal is a mobile telephone, a tablet computer, aportable computer, or a machine-type communication device.
 16. A methodof operating a radio receiver circuit configurable to operate in acarrier-aggregation (CA) mode, wherein the radio receiver circuit is toreceive a plurality component carriers (CCs) and in a non-CA mode,wherein the radio receiver circuit is to receive a single frequency CC,wherein the radio receiver circuit comprises: a first receive pathoperatively connected to an antenna; a second receive path operativelyconnected to the same antenna; and a processing circuit operativelyconnected to the first receive path and the second receive path; whereinthe method comprises controlling, in the CA mode and by the processingcircuit, the first receive path to receive a first CC of said pluralityof frequency bands and the second receive path to receive a second CC,separate from the first CC, of said plurality of CCs; and selectivelycontrolling, in the non-CA mode and by the processing circuit, the firstreceive path and the second receive path to both receive the same singleCC.
 17. A non-transitory computer-readable medium comprising, storedthereupon, a computer program product comprising computer program codethat, when executed by a processing circuit of a radio receiver circuitconfigured to operate in a carrier-aggregation (CA) mode, wherein theradio receiver circuit is to receive a plurality component carriers(CCs) and in a non-CA mode, wherein the radio receiver circuit is toreceive a single frequency CC, wherein the radio receiver circuitcomprises a first receive path arranged to be operatively connected toan antenna, a second receive path arranged to be operatively connectedto the same antenna, and the processing circuit operatively connected tothe first receive path and the second receive path, causes theprocessing circuit to: in the CA mode, control the first receive path toreceive a first CC of said plurality of CCs and control the secondreceive path to receive a second CC, separate from the first CC, of saidplurality of CCs; and in the non-CA mode, selectively control the firstreceive path and the second receive path to both receive the same singleCC.